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 <head>
  <title>HPSF</title>
 </head>

 <body>
  <div>
   <p>Processes streams in the Horrible Property Set Format (HPSF) in POI
    filesystems. Microsoft Office documents, i.e. POI filesystems, usually
    contain meta data like author, title, last saving time etc. These items
    are called <strong>properties</strong> and stored in
    <strong>property set streams</strong> along with the document itself. These
    streams are commonly named <tt>\005SummaryInformation</tt> and
    <tt>\005DocumentSummaryInformation</tt>. However, a POI filesystem may
    contain further property sets of other names or types.</p>

   <p>In order to extract the properties from a POI filesystem, a property set
    stream's contents must be parsed into a {@link
    org.apache.poi.hpsf.PropertySet} instance.  Its subclasses {@link
    org.apache.poi.hpsf.SummaryInformation} and {@link
    org.apache.poi.hpsf.DocumentSummaryInformation} deal with the well-known
    property set streams <tt>\005SummaryInformation</tt> and
    <tt>\005DocumentSummaryInformation</tt>. (However, the streams' names are
    irrelevant. What counts is the property set's first section's format ID -
    see below.)</p>

   <p>The factory method {@link org.apache.poi.hpsf.PropertySetFactory#create}
    creates a {@link org.apache.poi.hpsf.PropertySet} instance. This method
    always returns the <strong>most specific property set</strong>: If it
    identifies the stream data as a Summary Information or as a Document
    Summary Information it returns an instance of the corresponding class, else
    the general {@link org.apache.poi.hpsf.PropertySet}.</p>

   <p>A {@link org.apache.poi.hpsf.PropertySet} contains a list of {@link
    org.apache.poi.hpsf.Section}s which can be retrieved  with {@link
    org.apache.poi.hpsf.PropertySet#getSections}. Each {@link
    org.apache.poi.hpsf.Section} contains a {@link
    org.apache.poi.hpsf.Property} array which can be retrieved with {@link
    org.apache.poi.hpsf.Section#getProperties}. Since the vast majority of
    {@link org.apache.poi.hpsf.PropertySet}s contains only a single {@link
    org.apache.poi.hpsf.Section}, the convenience method {@link
    org.apache.poi.hpsf.PropertySet#getProperties} returns the properties of a
    {@link org.apache.poi.hpsf.PropertySet}'s  {@link
    org.apache.poi.hpsf.Section} (throwing a {@link
    org.apache.poi.hpsf.NoSingleSectionException} if the {@link
    org.apache.poi.hpsf.PropertySet} contains more (or less) than exactly one
    {@link org.apache.poi.hpsf.Section}).</p>

   <p>Each {@link org.apache.poi.hpsf.Property} has an <strong>ID</strong>, a
    <strong>type</strong>, and a <strong>value</strong> which can be retrieved
    with {@link org.apache.poi.hpsf.Property#getID}, {@link
    org.apache.poi.hpsf.Property#getType}, and {@link
    org.apache.poi.hpsf.Property#getValue}, respectively. The value's class
    depends on the property's type. <!-- FIXME: --> The current implementation
    does not yet support all property types and restricts the values' classes
    to {@link java.lang.String}, {@link java.lang.Integer} and {@link
    java.util.Date}. A value of a yet unknown type is returned as a byte array
    containing the value's origin bytes from the property set stream.</p>

   <p>To retrieve the value of a specific {@link org.apache.poi.hpsf.Property},
    use {@link org.apache.poi.hpsf.Section#getProperty} or {@link
    org.apache.poi.hpsf.Section#getPropertyIntValue}.</p>

   <p>The {@link org.apache.poi.hpsf.SummaryInformation} and {@link
    org.apache.poi.hpsf.DocumentSummaryInformation} classes provide convenience
    methods for retrieving well-known properties. For example, an application
    that wants to retrieve a document's title string just calls {@link
    org.apache.poi.hpsf.SummaryInformation#getTitle} instead of going through
    the hassle of first finding out what the title's property ID is and then
    using this ID to get the property's value.</p>

   <p>Writing properties can be done with the classes
    {@link org.apache.poi.hpsf.MutablePropertySet}, {@link
    org.apache.poi.hpsf.MutableSection}, and {@link
    org.apache.poi.hpsf.MutableProperty}.</p>

   <p>Public documentation from Microsoft can be found in the  <a 
    href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/stg/stg/properties_and_property_sets.asp"
    target="_blank">appropriate section of the MSDN Library</a>.</p>

   <div>
    <h2>History</h2>

    <dl>
     <dt>2003-09-11:</dt>

     <dd>
      <p>{@link org.apache.poi.hpsf.PropertySetFactory#create(InputStream)} no
       longer throws an
       {@link org.apache.poi.hpsf.UnexpectedPropertySetTypeException}.</p></dd>
    </dl>
   </div>


   <div>
    <h2>To Do</h2>

    <p>The following is still left to be implemented. Sponsering could foster
     these issues considerably.</p>

    <ul>

     <li>
      <p>Convenience methods for setting summary information and document
       summary information properties</p>
     </li>

     <li>
      <p>Better codepage support</p>
     </li>

     <li>
      <p>Support for more property (variant) types</p>
     </li>

    </ul>

   </div>

   <p>
    @author Rainer Klute (klute@rainer-klute.de)
   </p>
  </div>

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